In the art of closed loop film or tape information storage and retrieval systems, such as a photo-optically controlled pattern generator, or the like, a relatively large number of turns or strata of film strip segments or layers may overlie one another in the sub-pathway along the pathway chosen for closed loop film storage and transport. In a closed loop film transport system, the individual film layers in the sub-pathway are typically generally continuously being translated. Thus, the translation travel rate of each film layer in the sub-pathway is slightly different from that of adjacent such film layers with sub-pathway tape segment speeds varying progressively as one proceeds from outward segments inwardly.
In, for instance, a photo-optical closed loop system of the type employing edge perforated film (for example, of the conventional 35 mm type), a single drive capstan unit can be used to move the closed film loop even when the number of individual film layers is relatively large; for example, in excess of 50. However, with increasing numbers of film layers in the sub-pathway, there is a definite tendency for adjacent film layers to seize and bind against one another so that film transport cannot be effectuated by the capstan drive thus resulting in an equipment operational failure. The exact conditions causing such a film seizure are somewhat variable, apparently, being dependent upon many factors including, for examples, film surface characteristics, film transport speeds, amount of air present between adjacent layers, environmental temperature and humidity conditions, and the like. The manner, and especially the direction, of film travel relative to the sub-pathway in the system affects whether or not film seizures will occur. When, for example, the number of sub-pathway adjacent film layers falls above about 50, film seizures can apparently readily occur, which creates severe operating problems, especially with automated equipment.
Previous efforts to alleviate this problem have involved hand manipulation of film layers to keep same in a "free" condition which is considered an undesirable solution because of safety considerations and because of the need to minimize continuous operator attention during machine operation. No mechanical or pneumatic contrivances are known which will automatically eliminate film seizure when a film strip is moved from the inside to the outside of a sub-pathway, such as the pathway used in the memory center of a pattern reader and controller for a circular knitting machine, and where the film loop perimeter is very large compared to that of the sub-pathway.